The importance of highly functional input devices for computing devices such as computers has grown in concert with the rise in functionality and speed of the computing devices themselves. One popular computer input device is the mouse. User-directed motion of a mouse is translated into motion of a cursor or other pointer on the computer display, and buttons, wheels, etc. on the mouse are utilized to, for example, select various images on the display. Conventional mechanical mice (or mouses) incorporate a roller ball. Sensors within the mouse detect the motion of the ball as the mouse is manipulated. However, the moving parts of mechanical mice frequently become contaminated with dust or other particulates, deleteriously impacting mouse performance.
One way to overcome the shortcomings of mechanical mice is to use optical sensors within the mouse to detect its motion. A mouse incorporating optical sensors, frequently termed an “optical mouse,” includes a light source, such as a laser or light-emitting diode, and a photosensor. Light from the light source is transmitted toward and reflects off of a surface as the mouse is moved thereover and the photosensor detects the reflected light many times a second. Movement of the mouse is determined based on slight changes in the images created by the reflected light.
While optical mice have compensated for many of the shortcomings of mechanical mice, they have deficiencies of their own. In particular, the motion of an optical mouse over optically specular, transparent, or highly reflective surfaces is difficult to determine with a high degree of accuracy. Moreover, the light source requires a relatively large amount of power, which may compromise the lifetime of battery-powered wireless mice.